1. Field of the Invention
The present invention relates to an optical disc player, and more particularly, to a loading motor control device of an optical disc player, which controls operation of a loading motor that conveys a tray to be loaded or unloaded, and controls motion of a pickup deck.
2. Description of the Related Art
An optical disc player is an apparatus to record and reproduce information on and from a recording medium, such as a compact disc (CD), a digital video disc (DVD), etc., using an optical beam. FIG. 1 is an exploded perspective view of a conventional optical disc player. FIG. 2 is a partially enlarged perspective view of FIG. 1 for explaining operations of a conventional pickup deck lift device, including a conventional loading motor control device, and FIG. 3 is a reference drawing for explaining working modes of the conventional loading motor control device.
Referring to FIGS. 1 and 2, a conventional optical disc player has a housing 10 including a main frame 11, a cover plate 12 that is assembled onto the main frame 11, and a tray 20 to carry a disc 1 into and out of the housing 10. The disc 1 carried in by the tray 20 is placed onto a turntable 33 that is connected to a spindle motor 32. The spindle motor 32 is mounted on a pickup deck 30 that is connected to the main frame 11. An optical pickup 34, to record and reproduce information on and from the disc 1, is also mounted on the pickup deck 30.
The tray 20 includes a disc container 21 to place the disc 1 on. The tray 20 is moved in or out by a tray-conveying device that includes a tray-conveying rack gear 22, a pinion gear 42, a pulley gear 44, a belt 46, and a loading motor 48. The tray-conveying rack gear 22 is provided on a bottom surface of the tray 20, in a longitudinal direction thereof. The pinion gear 42 is mounted on the main frame 11, and engages the tray-conveying rack gear 22. The pulley gear 44 is also mounted on the main frame 11, and engages the pinion gear 42. The loading motor 48, which is also mounted on the main frame 11, drives and rotates the pulley gear 44 via the belt 46. Further, upper guides 14 and lower guides 16, to guide the tray 20 in and out of the housing 10, are provided on the main frame 11.
The pickup deck 30 has a rear end that is hinged with the main frame 11, and a front end that is engaged with a lift device mounted on the main frame 11. The pickup deck lift device includes a sliding cam 50 that is movably mounted on the main frame 11, and a pair of protrusions 36 that are formed on the front end of the pickup deck 30. Each of the protrusions 36 is respectively inserted into each of a pair of cam grooves 56 formed in the sliding cam 50. The protrusions 36 slide along the cam grooves 56. Specifically, the cam groves 56 have traces to raise and lower the protrusions 36 so that the protrusions 36 slide along the traces of the cam grooves 56 while the sliding cam 50 moves in a predetermined direction. In accordance with such sliding motions of the protrusions 36 along the cam grooves 56, the pickup deck 30 moves up and down.
The sliding cam 50 is moved by the loading motor 48 of the above-described tray-conveying device. A cam-conveying rack gear 52 is provided at an end of the sliding cam 50, and selectively engages the pinion gear 42 of the tray-conveying device to move the sliding cam 50. Further, there is provided a pair of projections, to serve as first and second guide pins 54 and 55, on an upper surface of the sliding cam 50, each of which is inserted into a corresponding guide groove (not shown) provided at the bottom of the tray 20.
In addition, the conventional optical disc player includes a control device to control the loading motor 48 while the disc 1 is loading and unloading. A conventional loading motor control device includes first and second switches, 67 and 68 respectively, mounted on the main frame 11, and first and second operation plates, 57 and 58 respectively, provided on the sliding cam 50. In accordance with motions of the sliding cam 50, the first and second operation plates 57 and 58 respectively activate the first and second switches 67 and 68.
Operation of the conventional optical disc player will be described with reference to FIGS. 1 to 3. Positions A1 to A5 correspond, respectively, to modes A1 to A5. When the tray 20 is in an open state, the sliding cam 50 is completely moved in the direction of arrow D, as shown in FIG. 2, and the protrusions 36 are located at lower portions of the cam grooves 56. Accordingly, the front end of the pickup deck 30 is in a lowered position. Further, the cam-conveying rack gear 52 is out of mesh with the pinion gear 42. This tray-open state is depicted as mode A1 in FIG. 3. In mode A1, the first switch 67 is pressed by the first operation plate 57, and produces a first control signal with which a system control unit (not shown) detects the open state of the tray 20.
After the disc 1 is placed in the tray 20, and when a disc-loading signal is applied from outside, e.g., from a load/eject switch, the loading motor 48 rotates and the tray 20 moves into the housing 10. When the tray 20 moves into the housing 10 by a predetermined longitudinal distance, e.g., about 8 mm, a first guide groove (not shown), provided on the bottom of the tray 20, interferes with the first guide pin 54. Accordingly, the sliding cam 50 moves by a first latitudinal distance in the direction of arrow U in FIG. 2. As the first operation plate 57 also moves by the first latitudinal distance in accordance with the motion of the sliding cam 50, the first switch 67 is switched off, and each of the protrusions 36 is placed in position A2, as shown in FIG. 3. At this time, both of the switches 67 and 68 are in off states. During the period when each of the protrusions 36 is moving from position A1 to position A2 in FIG. 3, typically, a pulse voltage with a predetermined duty cycle is applied to the loading motor 48 to prevent the tray 20 from inclining due to a sudden motion of the tray 20. When each of the protrusions 36 reaches position A2 and the first switch 67 turns off, however, a normal DC voltage is applied to the loading motor 48 so that the tray 20 moves constantly.
When the tray 20 accommodating the disc 1 is completely inserted into the housing 10, a second guide groove (not shown), provided on the bottom of the tray 20, interferes with the second guide pin 55, and the sliding cam 50 additionally moves a second latitudinal distance in the direction of the arrow U. In accordance with the additional motion of the sliding cam 50, the cam-conveying rack gear 52 engages the pinion gear 42. At this time, each of the protrusions 36 reaches position A3 in FIG. 3. As the loading motor 48 continues to rotate, the sliding cam 50 continues to move in the direction of arrow U, and thus the protrusions 36 ascend along the cam grooves 56 to raise the pickup deck 30.
When each of the protrusions 36 completes the ascending motion and reaches position A4 in FIG. 3, the pickup deck 30 is completely lifted, and the disc 1 is placed on the turntable 33. As previously noted, the turntable 33 is connected to the spindle motor 32, which is mounted on the pickup deck 30. At this time, the second switch 68 is switched on by the second operation plate 58 to produce a second control signal, so that the system control unit (not shown) detects that the tray 20 is closed and the disc 1 is loaded. Thereafter, the loading motor 48 continues to rotate, to keep moving the sliding cam 50, until each of the protrusions 36 reaches position A5 in FIG. 3.
When a disc-unloading signal is applied from outside, e.g., the load/eject switch, while the tray 20 is in the closed state, the loading motor 48 rotates inversely, and accordingly, the sliding cam 50 moves in the direction of arrow D. Thereafter, unloading operations are performed inversely to the loading operations as described above.
As described herein above, the conventional loading motor control device includes a pair of switches 67 and 68 and a pair of operation plates 57 and 58 to detect whether the tray 20 is in an open state or in a closed state, and to control the loading motor 48 in two modes, i.e., a tray open mode and a tray close mode. As the control modes of the conventional loading motor control device are very simple and are limited corresponding to the number of switches, it is difficult to control the loading motor 48 at various time and in various ways. For example, while the pickup deck 30 is being raised or lowered, a much higher voltage should be applied to the loading motor 48. However, such voltage control is difficult with the conventional loading motor control device. Further, it is difficult to detect accurate timing with limited position information, and it is difficult to adequately control duty cycles of control signals. Moreover, to increase the number of control modes, the structure of the device becomes complicated because additional switches and operation plates must be included. Furthermore, in the conventional loading motor control device, since the operation plates 57 and 58 interfere with upper portions of the switches 67 and 68, respectively, to switch the switches 67 and 68, it is difficult to determine relative positions and heights between the operational plates and the switches.